Asteroid killing/deflection Mega Thread (Nuclear Bomb Saving Earth From an Asteroid)

[MaverickSawyer]

Essentially it would be a form of nuclear pulse propulsion. But I think Orion didn't actually intend to ablate away the pusher plate, just use it to direct plasma from the detonation.

Orion was also supposed to use "shaped charge" nuclear devices to direct the plasma at the pusher plate.

What I meant was that you would use a string of closely-spaced nuclear detonations for thrust generation, regardless of the source of the "exhaust."

 

[RisingFury]

It isn't only about applying energy, but how that energy is applied (and also other 'secondary' factors- interaction with fragments).

A salvo of less intensive detonations might be preferable to a single more intensive detonation for this reason.

Also, you can't say that it would cause the object to disentegrate, and neither can I. There simply isn't enough knowledge about the matter to say so, and it is very likely to be context sensitive.

Perhaps one way of studying the propensity of bolides to disintegrate when imparted with force, would be to study historical impact events on the object and their effects on the object.

Of course, the intended effect is still achieved even if the fragments separate, as long as enough dV is imparted to them. But there might be reasons that could make it an unwanted scenario.

A more 'common' issue might be particles or smaller fragments 'rebounding' off the object during/after ablation.

I bow before your infinite knowledge and experience in many branches of Physics and asteroid deflection.

 

[T.Neo]

I bow before your infinite knowledge and experience in many branches of Physics and asteroid deflection.

I am sorry?

If you do not like what I say, then use proper arguments against it, don't insinuate that you think I think I know everything.

Or that you think I know nothing at all, just because you do not like what I say.

 

[Sky Captain]

Another advantage of deflecting asteorid with nuclear pulse propulsion is that there is no need to match velocity with it. Just set the warhead on a close flyby course that brings it few hundred meters or whatever distance is the optimal and set it off at right moment. Matching velocity with asteorid especially if it has elliptical or out of plane orbit would require lot of delta v maybe even too much for chemical rockets.

 

[Tychonaut]

So, more like an Orion drive? Makes a great deal of sense.

Using Orion pulse units instead of standard bombs might be an improvement. They're designed to deliver a great deal of thrust to a nearby object in a relatively controlled and directional way. Doesn't matter to the bomb if it's an oil-coated pusher plate or an asteroid.

Here's a twist. With all the research going into studies to deflect asteroids away from the Earth, I wonder if any nations are considering how equally easy/hard it would be to deflect an asteroid's trajectory toward the Earth? Would be easy to disguise such a mission as a research effort, I believe.
...

It would certainly be an inventive way to attract global rage.
Also, the spacecraft had better communicate on well-encrypted channels, or you're likely to find someone has hacked in and sent it tumbling out of control.
In any case, a nation capable of constructing the required launch vehicles and spacecraft probably already has copious quantities of more mundane weapons with which to bully its neighbors. Though suppose you have rockets and spacecraft, but nothing else which might be a weapon...Elon Musk, I'm on to your plan! :lol:

 

[RisingFury]

I am sorry?

If you do not like what I say, then use proper arguments against it

It isn't only about applying energy, but how that energy is applied (and also other 'secondary' factors- interaction with fragments).

Please, mathematically describe those interactions and application of energy. If you don't, then you might as well have pulled that statement out of your rear end.


There's actually good data to know that comets break up. We see it happen when they get close to the Sun and the melting breaks them apart or when they stray close to a planet and get torn up by gravity.

There's also good data to believe some asteroids are loosely bound or fractured. Martian moon Phobos has a giant crater on it and simulations suggest that had it been hit by a few degree higher angle, it would have been destroyed. It's highly probable that the impact left the asteroid fractured and loosely bound.

 

[T.Neo]

Using Orion pulse units instead of standard bombs might be an improvement. They're designed to deliver a great deal of thrust to a nearby object in a relatively controlled and directional way. Doesn't matter to the bomb if it's an oil-coated pusher plate or an asteroid.

The problem there is that Orion-type pulse units do not exist.

As far as we know. :shifty:

Please, mathematically describe those interactions and application of energy. If you don't, then you might as well have pulled that statement out of your rear end.

What needs to be mathematically described about "various phenomena can change the outcome"?

It is a matter of uncertainty, not certainty.

There's actually good data to know that comets break up. We see it happen when they get close to the Sun and the melting breaks them apart or when they stray close to a planet and get torn up by gravity.

There are different forces involved there though, gravity gradients and/or materials being melted/vaporised.

There's also good data to believe some asteroids are loosely bound or fractured. Martian moon Phobos has a giant crater on it and simulations suggest that had it been hit by a few degree higher angle, it would have been destroyed.

That's vaguely what I'm trying to get at; if the circumstances were different, there could have been a different outcome.

It's highly probable that the impact left the asteroid fractured and loosely bound.

But it would be nice to know what the dynamics of the actual internal structure are, no? Such data could assist the execution of asteroid mitigation simulations.

Alas, our recent Phobos probe is stuck in orbit around the Earth now. :dry:

 

[Urwumpe]

The problem there is that Orion-type pulse units do not exist.

As far as we know. :shifty:

Wrong, the kind of technology is actually already tested in the many thousand nuclear explosions that we did in the past decades.

 

[T.Neo]

Wrong, the kind of technology is actually already tested in the many thousand nuclear explosions that we did in the past decades.

Didn't Orion require a sort of "shaped charge" to direct the plasma against the pusher-plate?

Is this technology well known and just classified? And do we have any nuclear shaped charges lying around anywhere? :hmm:

 

[Tychonaut]

Didn't Orion require a sort of "shaped charge" to direct the plasma against the pusher-plate?

Is this technology well known and just classified? And do we have any nuclear shaped charges lying around anywhere? :hmm:

Here's the standard picture of an Orion pulse unit.

"Shaped charge" might be a bit of a misnomer. As I understand it (and of course I Am Not A Bomb Designer), the propellant is intended to become an expanding disc of plasma that distributes thrust somewhat evenly across the pusher plate, rather than the narrow jet of a typical shaped charge like a HEAT shell.
Apparently a more "focused" version of the pulse unit technology was pursued in the Casaba Howitzer project, sort of a weaponized counterpart of the propulsion pulse units. R&D on Casaba is said to have continued after Orion was cancelled, and into the SDI era. So it's possible this technology is more mature than we would guess.
I recommend this book for more on the history of Orion. Some of the project reports have been de-classified and can be hunted down on the net.

 

[Urwumpe]

The orion charges are directing most of the energy of the nuclear explosion towards the vessel by the nozzle shaped channel. This is essentially the same technology as used for thermonuclear bombs, but applied differently. In hydrogen bombs, the radiation channel is used for compressing and heating the fusion secondary charge.

It works by focusing the radiation of the explosion stronger towards the propellant as in the other directions, using the channel filler to create a plasma cloud that pushed the colder heavier propellant towards the spacecraft. The propellant also aids in blocking the radiation that is focused towards it, absorbing more of the energy.

(EDIT: I am no bomb physician either - but I learned a lot about the cold war, when it was still running)

 

[Pari]

Interesting read, thank you guys !

If an attempt to deflect an asteroid was done, would we know about it ?

And how long in advance should a rocket for instance to deflect it ?

 

[Loru]

Best option is half of orbital period before impact.

 

[RisingFury]

If an attempt to deflect an asteroid was done, would we know about it ?

You mean, if someone tried to do it in secret? Yes, we'd know about it. Asteroids don't change their orbits for no apparent reason...

 

[Urwumpe]

You mean, if someone tried to do it in secret? Yes, we'd know about it. Asteroids don't change their orbits for no apparent reason...

Also the energy costs for even a small change in velocity for an asteroid that matters is huge, and since you can't apply it perfectly, there would be a lot of light getting emitted if you try that.

 

[Tychonaut]

This describes a workshop about moving asteroids. Not for planetary defense purposes, but if you can learn to move asteroids for one reason, you can do it for any other. Some pdf and video files which may be of interest are available from the linked pages.

 

[T.Neo]

Why move asteroids to the vicinity around Earth?

It isn't like it is impossible to research or exploit (though that's another matter entirely) them elsewhere.

Johannesburg popped up at the gold deposits of the area; they didn't scoop the whole geological complex out of the ground and move it to Cape Town...

 

[orb]

Aviation Week: Planetary Defense Plans For Asteroids Form

 

[orb]

Aviation Week: New Technique For Asteroid Diversion:

Texas A&M University is leading a collaboration on a novel “soft-push” technique for diverting hazardous Near Earth Asteroids that is gathering maturity for a future orbital flight test.

NASA’s Ames Research Center and the King Abdulaziz City for Science and Technology in Saudi Arabia are collaborating with Texas A&M Aerospace Engineering Professor David Hyland, as he and his students seek a flight test opportunity as a secondary payload.

“I think it’s the real deal,” says Hyland, who began work on a strategy for gradually altering the course of a distant but threatening asteroid in 1997 while he chaired the department of Aerospace Engineering at the University of Michigan. As a professor of aerospace and physics at Texas A&M, he has encouraged his students to refine the effort, and they have settled on a diversionary strategy that would alter the path of a NEA barreling toward the Earth by changing its albedo, or reflectivity.

The change would be accomplished with an application of a light or dark surface coating, using an unpiloted probe hovering over the NEA. The strategy depends on a manipulation of the Yarkovsky force, or the thermal emission of protons from the dusk, or warmer, side of a rotating planetary body. It is thought that the emitted protons from a rolling NEA can exert a small propulsive force that could gently change its path.

Four years ago, Hyland began to ask students to develop a mitigation strategy and a flight test, an annual exercise that evolved into the proposed Apophis Mitigation Technology Mission (AMTM). The project borrows its name from 99942 Apophis, a 250-meter wide asteroid that in late 2004 created temporary alarm over the possibility of a regionally devastating collision with the Earth in 2029. Subsequent observations eased those concerns but raised the prospect that the Earth’s gravity would alter the path of Apophis just enough on that pass to set up a possible impact in early 2036.

Those concerns have since diminished as well, but the well-studied NEA offers a suitable test target, Hyland says.

The students responded to his challenge with the Surface Albedo Treatment Subsystem, a Triboelectric charging apparatus that could apply a light or dark powder coating on Apophis to alter its albedo enough to produce a three-Earth-radius dispersion by 2036.

{...}

 

[RisingFury]

I haven't found any papers as to how much force this would provide. I'm sure I could do the calculation myself, but it's at this point irrelevant. The big challenge is the coating. I also haven't found anything as to what the coating would be...

There's also this:

or the thermal emission of protons from the dusk

I think that's a mistake, I think they mean photons...


Assuming you have to bring the coating with you, if you take a sphere with a radius of 250 m and assume you want a 10 ton payload (spacecraft + coating), you'll need the coating to be in the thickness range of 0.01 mm!

Also, most asteroids are already quite dark and have a low surface albedo, which means the application of coating wouldn't mean much. Also, the asteroid needs to spin. I'm guessing the spin rate has an optimal value, but I'd have to do more calculations on that.

I'm guessing if the asteroid spins slowly or quickly, there won't be enough temperature differences to cause the effect.


I'm not convinced. I still think the gravitational tractor is a more reliable method.